In cutting operations, such as milling or hobbing processes to produce gears, it is known to utilize cutting tools wherein one or more cutting blades are positioned in and project from a cutter head. See, for example, U.S. Pat. Nos. 4,621,954 to Kitchen et al. or 5,890,846 to Clark et al.
Cutting blades are usually secured in position in a cutter head by one or more clamping screws. The clamping screws may be in direct contact with the cutting blades such as shown in U.S. Pat. Nos. 4,268,194 to Bloink et al. or 4,530,623 to Kotthaus. In other instances, clamping screws may contact a clamp block which in turn contacts a cutting blade as can be seen, for example, in the previously mentioned U.S. Pat. Nos. 4,621,954 or 5,890,846. With the clamp block arrangement, clamping forces can be spread out along the blade-clamp block interface instead of the point contact that occurs with direct contact between the clamp screw and cutting blade.
In either of the clamping arrangements discussed above or in other similar arrangements, loosening of one or more clamp screws (such as is done after sharpening in order to reposition a cutting blade to a proper height above the face of a cutter head) may result in a cutting blade becoming unstable in the cutter head. Once contact between the clamp screw (or the clamp block) and the cutting blade is lost, the cutting blade is free to move. Even after a cutting blade is correctly positioned in a cutter head, there is nothing to ensure the correct position will be maintained prior to contact by a clamp screw or clamp block. Thus, the slightest force introduced to the cutting blade or cutter head prior to contact may result in the cutting blade being moved to an undesired position and to the subsequent formation of a geometrically incorrect tooth surface on a gear.
One manner set forth to alleviate the above problem of unstable cutting blades in the unclamped position is disclosed in U.S. Pat. No. 4,197,038 to Hipp et al. wherein pretensioning elements are utilized to maintain position of a cutting blade prior to clamping. The pretensioning elements comprise a generally bracket-shaped (]) pressure member which is positioned adjacent a cutting blade. The pressure member is acted upon either by a spring-loaded stud or a profiled spring to apply an amount of force to the cutting blade to hold the cutting blade in position until clamped but yet allow the cutting blade to be axially repositioned in the cutter head as necessary.
A drawback of the above pretensioning arrangement is that it creates additional elements that must reside in the cutter head since in addition to clamp screws, a pressure member and a force providing member are also required. This not only results in a more complicated cutting tool, but it increases production costs and slows cutting tool assembly time.
It is an object of the present invention to provide a clamping screw that not only clamps a cutting blade in position in a cutter head but also serves to hold cutting blades in a pre-clamped position whereby a small force is provided by the clamp screw to hold the cutting blade against its reference surfaces in the cutter head. In the pre-clamped position, the cutting blade may be displaced linearly to its proper position in the cutter head.